Ground surface microtopography and vegetation patterns in a tropical peat swamp forest

In tropical peat swamp forests (PSF), the ground surface is covered with higher elevated surfaces, hummocks, and part of the year wet depressions, hollows. We present a detailed description of PSF floor microtopography combined with analysis of ground water table dynamics and the occurrence of vegetation in mixed swamp forest in Central Kalimantan, Indonesia. In the study area, hummocks and hollows were neither oriented in relation to the water flow nor did their spatial distribution seem to follow any other regularly repeated patterning. Combined data from long-term water table measurements and ground surface elevation mapping showed that for most of the year more than half of the soil surface is above the ground water table. The highest and lowest water table levels lasted a relatively short time with less fluctuation during higher than low water tables. Vegetation was concentrated on elevated surfaces such that tree seedlings were found at all elevations whereas mature trees were more abundant at higher elevations. We expect both flooding-induced oxygen deficiency in hollows and better nutrient availability in hummocks to steer the vegetation growth towards higher surfaces. The patterns of microtopography and vegetation between the areas closer to the margins versus the more central locations on the peat dome were similar.